White light interference microscope

Abstract

A white light interference microscope includes an imaging part taking interference images, a laser light source, a light receiving part receiving reflected light of laser beam from a sample via a confocal optical system and generating a light reception signal corresponding to the light receiving intensity of the reflected light, a focal calculation part calculating a focal position matching a focus of the objective lens with a surface of the sample based on the light reception signal at each height position of the stage or the objective lens, a focus adjustment part adjusting the height position of the stage or the objective lens to match with the focal position, and a first measuring part measuring the surface shape of the sample based on a plurality of interference images taken by the imaging part at a plurality of height positions defined within a height range including the focal position.

What is claimed is: 
     
       1. A white light interference microscope comprising:
 a stage on which a measuring object is placed; 
 a white light source that irradiates white light to the measuring object placed on the stage via an objective lens; 
 a branching optical system that branches the white light irradiated from the white light source into a reference light directed to a predetermined reference surface, and a measurement light directed toward the measuring object; 
 a camera that captures an interference image by receiving the reference light reflected by the reference surface and the measurement light reflected by the measuring object; 
 a laser light source that irradiates a laser beam directed to the measuring object via the same objective lens or a different objective lens; 
 a photodetector that receives a reflected light of the laser beam from the measuring object via a pinhole arranged in a confocal optical system including the objective lens, and generating a light reception signal according to a light receiving intensity of the reflected light; 
 a driving part that adjusts a relative height position of the stage with respect to the objective lens; and 
 a processor in communication with a memory, the processor being configured to execute instructions stored in the memory to: 
 calculate a focal position matching a focus of the objective lens with a surface of the measuring object based on the light reception signal generated by the photodetector with respect to receiving the reflected light of the laser beam from the measuring object via the pinhole arranged in the confocal optical system at each relative height position of the stage; 
 control the driving part to move the relative height position to the focal position by adjusting the relative height position of the stage; and 
 perform a first measurement processing which measures a surface shape of the measuring object based on a plurality of interference images captured by the camera, the camera receiving the reference light reflected by the reference surface and the measurement light reflected by the measuring object, at a plurality of height positions defined within a height range including the focal position. 
 
     
     
       2. The white light interference microscope according to  claim 1 , further comprising:
 a laser scanner scanning the laser beam irradiated from the laser light source on the surface of the measuring object in X-axis and Y-axis directions, 
 wherein the processor is configured to perform a second measurement processing which measures the surface shape of the measuring object based on the light receiving intensity of the reflected light of the laser beam scanned within a first scanning range by controlling the laser scanner. 
 
     
     
       3. The white light interference microscope according to  claim 2 , wherein the processor scans the laser beam within a second scanning range by operating the laser scanner in each height position of the stage at the time of calculation of the focal position, and the second scanning range is set narrower than the first scanning range. 
     
     
       4. The white light interference microscope according to  claim 3 , wherein the second scanning range in the Y-axis direction is set shorter than the first scanning range. 
     
     
       5. The white light interference microscope according to  claim 3 , wherein when the processor calculates the focal position, a distance of the height positions from each other at the time of changing the relative height position of the stage is set wider than in the case of measuring the surface shape of the measuring object by the first measurement processing. 
     
     
       6. The white light interference microscope according to  claim 1 , wherein after the calculation of the focal position, the processor generates an interference image via the camera in a state in which the relative height position of the stage is changed from a starting position with the focal position as a reference, and calculates a peak position of interference fringes from the interference image generated at each height position, and the height range is set as a range in which a pixel number, for which the peak position is calculated, is above a predetermined first threshold. 
     
     
       7. The white light interference microscope according to  claim 1 , wherein after the calculation of the focal position, the processor generates an image based on the light reception signal in a state in which the relative height position of the stage is changed from a starting position set with the focal position as a reference, and generates pixel data corresponding to the light reception signal generated in the photodetector for a plurality of pixels in an image generated at each height position, and the height range is set in a range in which all values of the plurality of pixel data are below a predetermined second threshold. 
     
     
       8. The white light interference microscope according to  claim 5 , wherein in the case in which a distance of the height positions from each other at the time of changing the relative height position of the stage is set as the height range, the processor sets wider than in the case of measuring the surface shape of the measuring object. 
     
     
       9. The white light interference microscope according to  claim 5 , wherein the processor sets the focal position as the starting position. 
     
     
       10. The white light interference microscope according to  claim 5 , wherein the processor sets a range which is partitioned at an upper limit position set to be more than the focal position, and at a lower limit position set to be less than the focal position, and after the lower limit position is set, the upper limit position is set. 
     
     
       11. The white light interference microscope according to  claim 10 , wherein the processor divides the distance between the upper limit position and the lower limit position in an equal interval in the state in which the upper limit position and the lower limit position are set, and sets each height position of the stage when measuring the surface shape of the measuring object. 
     
     
       12. The white light interference microscope according to  claim 1 , wherein after calculating the focal position, the processor adjusts brightness of the white light source based on interference images captured by the camera, and among the interference images captured by the camera at each height position by changing the relative height position of the stage from the starting position set with the focal position as a reference by controlling the driving part, the processor extracts the interference images including the brightest pixel, and adjusts the brightness of the white light source in a range in which the brightness of each pixel in the interference images is not saturated. 
     
     
       13. The white light interference microscope according to  claim 12 , wherein the processor sets the focal position as the starting position.